The phenomenon of fouling corresponds to spontaneous colonization and accumulation of microorganisms, algae and animals on surfaces immersed for a variable period of time in a freshwater environment or in a seawater environment. Fouling is a significant nuisance, in particular for watercraft, because by deteriorating the surface of the hulls, it leads to an increase in maintenance costs and presents resistance to the forward movement of the watercraft, resulting in overconsumption of fuel and a reduction in speed.
To overcome this phenomenon, paints incorporating tributyltin, a very effective biocide, have been used for a number of years. Unfortunately, this molecule and its degradation products, released in the seawater environment, seriously affect ecosystems, which has resulted in their total prohibition since 2008. In addition, these residues, including tin, remain in the sediments of ports and immersion sites of dredged slurry.
By replacing tributyltin, a certain number of products that are in principle less toxic have been used: these are for the most part biocidal molecules of low molecular weight such as halogenated molecules, for example chlorinated derivatives (sold under the names: Seanine 211, Kathon 5287, Dichlofluanid, Daconil, Thiodan, Duron, etc.), metal-based derivatives such as zinc or copper (Zinc pyrithione, Ziram, Dithane, etc.) or nitrogenated heterocyclic derivatives (Irgarol 1051), which are incorporated in the matrix of the coating.
These molecules are, however, slowly released into the aquatic environment, thus producing, by accumulation, a certain toxicity in the environment. The European program REACH encourages abandonment of the addition of any organic product (of the herbicide or pesticide type, such as the derivatives described above) in the antifouling paint formulations. In addition, silicone-based paints have been developed, and admittedly demonstrate efficacy in the antifouling field, but have limited applicability, in particular due to their high production costs.